Rapid access to a selected segment of a strip information carrier

ABSTRACT

For lengthwise transit of a film strip from one frame at a fixed station, to bring any other selected frame thereto, a counter is charged with the initial number of frames that must pass the station. A pulse is produced as each frame passes the station, to count down the counter. The pulses are also integrated to produce a true strip speed signal. With the use of the charge on the counter, a demand value signal is produced, corresponding to a constant fast velocity for all frames that must pass the station in excess of a predetermined number, and therebelow, to a decreasing velocity proportional to number of frames still to pass. The strip drive is energized according to the difference between true and demand values, in a manner tending to maintain that difference at zero.

United States Patent [W Stalnert [451 Apr. 17, 1973 [5 RAPID ACCESS TO A SELECTED OTHER PUBLICATIONS E i L OF A STRIP INFORMATION Halthill, M. 0., and Daniels, D. V.; Track-Accessing Servo System"; in IBM Technical Disclosure Bulletin; [75] Inventor: Jan-Christer Stalnert, Linkoping, Vol. 9. N0. 12,May, 1967. pp. l694-1695 Sweden Bradley, E. F., Direct Access Tape Control System"; [73] Assignee: Saab-Scania Aktiebolag, Linkoping, 3 gg i g Buncun Sweden 22 Filed: Dec. 21 1970 Primary Examiner-Paul .l. Henon Assistant Examiner-Melvin B. Chapnick (2] 1 P 99,849 Attorney-Ara Milton Jones [30] Foreign Application Priority Data [57] ABSTRACT Dec. 22, 1969 Sweden ..l7680 For lengthwise transit ofa film strip from one frame at a fixed station, to bring any other selected frame 9 thereto, a counter is charged with the initial number [is] new ofat'r'siijiiiiii'.iiiiiiiiiiazrsyi'as 174.. C- of frames that must pass the A pulse 15 179/1002 178/6 6 P 6.6 353/26 produced as each frame passes the station, to count down the counter. The pulses are also integrated to [56] References Cited produce a true strip speed signalv With the use of the charge on the counter, a demand value signal is UNITED STATES PATENTS produced, corresponding to a constant fast velocity for all frames that must pass the station in excess of a 522:: predetermined number, and therebelow, to a decreaszjamime 11/1957 House .'.'.3 i6/'174,| c it mg vekchy P 9 T of frames 2367,79; 1959 Goldberg cl 3| "MO/174'. C x pass. The strip drive is energized according to the dif- 3941.134 6H9; Gams a 3L H 340/1741 C X ference between true and demand values, in a manner 3,|9l 1)06 6/ 965 Avakian r "340/1725 X tending to maintain that difference at zero. 3.36S 702 [H968 Healwole l ..340/l72.5 3,484,751 12/1969 Cameron et al ..340/l72.5 3,641,504 2/1972 Sidline ..340/172.5 l2 Claims, 5 Drawing Figures DlREClFUN GFSTER ANALOGUE ICONVFRTU? DIGITAL TQUL VA L UL TKAMNXALK BRAKE S l G NA L TRANSIXAIK PATENTEUAPR 1 11m 3.728.685

SHEET 1 OF 3 T FEED AND FRAME BRAKE HOLDING- CONTROL DIRECTION 55E REGISTER I COMPUTER 5 [K K ,4 5mm DIGITAL TRUE FRAME 596 mm COUNTNG fib gz TKZNEEJZQ REGISTE 35 4O FRAME BRAKE 'coumme LOGIC TRANSDULER lNVENTOR PATENTEU APR 1 7 75 SHEET 2 BF 3 IIIJ NEPDQZOU Arrow.

RAPID ACCESS TO A SELECTED SEGMENT OF A STRIP INFORMATION CARRIER This invention relates to a method and means for effecting rapid lengthwise motion of an information carrier strip, and for stopping the strip smoothly and accurately after it has been moved through exactly a preselected number of distance units; and the invention is more particularly concerned with accurate control of rapid lengthwise motion of a strip of photographic film or similar material to bring it from a position at which one of a series of adjacent frames or other uniform and consecutive segments along its length is at a relatively fixed reading station, to a position in which any selected one of its other frames or segments is at said reading station.

US. Pat. No. 3,478,326, to S. E. Bourghardt, discloses one type of apparatus in which the method and means of the present invention has particular utility. That patent relates to a device for assembling in an instruction memory a so-called instruction word to be supplied to an apparatus controlled by logic circuits.

The nature of that device in its relationship to the present invention can be best understood by reference to a specific example of it in one of its applications. Considering it as applied to a hospital record system involving apparatus controlled by logic circuits, the means for giving instructions to the apparatus can comprise a panel on which there is a name plate for each of a number of patients, a name" pushbutton adjacent to each name plate, an image screen around which there are a plurality of column" and line pushbuttons, and other pushbuttons signifying various part instructions, including a GO button which is used to signify to the apparatus that assembly of an instruction word has been completed.

When an instruction is to be given to the apparatus concerning a patient whose name appears on a name plate, the name" pushbutton for that patient is pressed, and a partial instruction corresponding to the selected patient named is stored in the temporary memory unit. At the same time there appears on the image screen a list of departments which might be concerned with the instructions about to be given, arranged in columns and rows. Column" and "row" pushbuttons around the image screen are pressed according to the column and row of the list in which the selected department appears. Actuation of the last mentioned pushbuttons stores a partial instruction in the temporary memory unit associated with the panel and brings into view on the screen a new image presenting another category of partial instructions, as for example, a list of the main parts of the human body, again arranged in columns and rows. Pressing pushbuttons for the column and row of a selected part of the body, such as the abdominal cavity, stores a further partial instruction and brings to the image screen a new category of items, which may be a list of the organs in the abdominal cavity. Again pushbuttons are pressed corresponding to the column and row in which a selected organ appears.

In this manner a complete instruction is assembled by a process of organized selection from a large number of categories of partial instructions. Each actuation of a pushbutton or pushbuttons brings into view on the image screen a new category of partial instructions, selected by the apparatus on the basis of the partial instruction signified by the particular pushbuttons that have been actuated. At the same time, the partial instruction signified by each pushbutton actuation is temporarily stored in the memory unit associated with the panel. When the instruction is completely assembled, the GO" button is pressed to signify that no further categories of partial instructions need be displayed, and to feed the assembled instruction from the memory unit into the executing apparatus.

It will be apparent that apparatus of the type just described can be applied to all sorts of record keeping and computing tasks, as well as to tasks related to data and information retrieval, inventory control, identification and analysis, reservation booking, etc.

In the above mentioned patent there is disclosed a modified form of apparatus in which instruction categories are stored on successive frames along the length of a film strip, and the film strip is moved as required to bring each selected frame to a position in which the image thereon can be projected onto the image screen. In such a machine the sequence in which partial instructions may be given cannot be anticipated, and therefore each frame of film must be coded in some manner to which the machine can respond, and the film must be moved lengthwise back and forth through different distances to bring successively selected frames thereof into position to be projected onto the image screen.

Since two successively selected frames of the film strip may be at some distance from one another along the length of the strip, it is essential that the film moving apparatus provide for lengthwise motion of the strip at the fastest possible speed, in order to avoid undue delay between the input of successive partial instructions. Nevertheless, motion of the strip must be stopped smoothly and gently, with due regard to the comparatively low strength of film and the inertia of the coiled portions ofthe film and their carriers.

Furthermore, the film should be stopped accurately, with the selected frame squarely aligned with the image screen. In a known system of film frame display such accurate stopping of the film does not occur, and the selected frame appears to overshoot the image screen slightly and then move back into projecting position. Such overshooting and reversal of motion is not only wasteful of time but is distracting and tiring to the operator.

With the foregoing considerations in mind it is a general object of the present invention to provide a method and means for rapidly and accurately moving a film strip to cause selected non-consecutive frames that may be spaced apart in either direction along the length of the strip to be brought to, and precisely stopped at, a predetermined reading station.

it is also an object of this invention to continuously accommodate the speed of strip advance in such apparatus to the linear distance through which the strip remains to be fed, to avoid abrupt accelerations and decelerations of the strip that might break it or deform it.

Since apparatus of the type here under consideration must be capable of use with very long strips of film or with other strip-form record material, it is necessary that the strip be coiled on bobbins and that lengthwise motion be imparted to the strip by rotation of the bobbins. However, the radius of the coil on each bobbin is constantly varying as strip is fed onto or off of it, and therefore there is a constantly changing relationship between the rate of rotation of the bobbin drive and the rate of lengthwise motion of the strip. If the bobbins were driven at a fixed speed of rotation, the resulting rates of lengthwise strip motion could be intolerably high or undesirably low near the ends of the strip.

With this in mind it is another object of this invention to provide apparatus of the character described having a pair of reversible motors for its bobbin drive and means for controlling the motors by reference to the rate of linear travel of the strip and the number of units of length through which the strip remains to be moved, thus automatically accommodating the varying radii of the strip coils.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the precise method of practicing the invention and in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of the embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIG. 1 is a more or less diagrammatic view of film feeding apparatus embodying the principles of this invention, in part a diagrammatic perspective view of the mechanical portions of the apparatus and in part a block diagram;

FIG. 2 is a graph of variation of strip feed velocity versus frames remaining to be traversed, illustrating the operation of apparatus embodying the principles of the invention;

FIG. 3 is a more detailed block diagram of the main components of the control apparatus for the strip mow ing means;

FIG. 4 illustrates a portion of a film strip and shows the coded marks thereon in their cooperation with photoelectric sensors in the apparatus and in their relation to signals which are produced by the coaction of the marks with the sensors and which appear at different points in the apparatus illustrated in H6. 3; and

FIG. 5 is a diagram showing how the demand value for feeding velocity can vary with the number of frames remaining to be fed.

Referring now more particularly to the accompanying drawings, the numeral 4 designates generally an electromechanical apparatus for effecting lengthwise motion of an information carrier strip 5, here shown as a strip of film on which there are lengthwise adjacent image frames 6 that define uniform units of strip length. The electromechanical apparatus 4 so moves the strip 5, at each transit thereof, as to bring a selected frame 6 to a predetermined reading or display station in which that frame is projected onto an image screen 7. The apparatus 4 is controlled by an electronic apparatus 8 which is associated with a computer 9.

ELECTROM ECHANICAL APPARATUS 4 The strip 5 is housed in a cartridge 10 which can be interchangeable with other similar cartridges and which has an accurately defined position in the electromechanical apparatus. In the cartridge there are a pair of bobbins ll and 12 upon which the strip is coiled. As viewed from above, the cartridge is in the form of a hollow rectangle, with a chamber 13 at each side thereof in which one of the bobbins is housed and with front and rear channel-like or tubular portions 14 which connect the bobbin chambers. The strip extends lengthwise between the bobbins through the front channel-like portion, being trained over hourglass shaped pulleys 15 which contact only its opposite edge portions and thus avoid wear on its image carrying surface.

The front and rear walls of said front channel-like portion have aligned apertures, as at 16, to provide a projection window with which a single frame of film can register for projection onto the image screen. A projection lamp 17, a condenser 18 and a projection lens 19 are aligned with the projection window for projecting onto the image screen 7 the frame of film that is in register with the window. The light beams through the film are reflected onto the screen 7 by means of oblique mirrors 20 and 21, the mirror 20 being mounted within the space between the channel-like portions 14 of the cartridge. The projection window 16 thus defines the reading or display station to which each selected frame must be brought when the strip is moved by the apparatus.

For each of the bobbins l1 and 12 there is a reversible electric drive motor 22, 23, and each motor drives its bobbin through a magnetic coupling 24, 25.

Each frame of the film is assigned a number, and the numbers run consecutively so that lengthwise movement of the strip in one direction can be regarded as increasing" motion and in the opposite direction as decreasing" motion. The motor 22 can be regarded as an increasing motor, since it feeds the strip in the increasing direction when it is running in its forward direction of operation. Similarly, the motor 23 is the decreasing" motor since it feeds the strip in the decreasing direction when it is in forward operation. Each of the reversible motors can perform a braking or retarding function when energized for running in its reverse direction.

Each image frame on the film terminates at a distance from one edge of the strip, and in this marginal space the strip has a code mark 26 adjacent to each frame. The code marks are identical for all of the frames except the one at each end of the strip, said end frames being given special coded marks which signify strip end." As shown in H0. 4, each of the ordinary code marks 26 has a much flattened T-shape, comprising a longer upper bar or dash 26a centered on its film frame and a shorter bar or dash 26b centered therebeneath. Two photoelectric sensors 27 and 28 are arranged to detect the respective bars 260 and 26b of the code marks for the film frames and to send to the electronic unit eight pulses that denote the passing of the code marks, as described hereinafter.

While a single bar code mark and a single photocell could be used for the purpose, the dual photocells 27 and 28 are better capable of discriminating between film end marks and ordinary frame marks, and in cooperation with the dual code marks 26a and 26b they provide increased security of code mark detection and produce a higher pulse frequency that is advantageous in the processing of the signals.

Two frame centering photocells 29 and 30 are arranged to detect only the opposite end portions of the longer bar 26a of each code mark and are employed in frame holding. The frame is in proper position when its code mark is blanking equal areas of the two cells 29 and 30.

ELECTRONIC APPARATUS GENERAL The photocells 27 and 28, in their cooperation with the code marks 26a and 26b, produce pulse signals that are delivered to the electronic apparatus 8, and such signals cause that apparatus to produce certain outputs that are utilized in controlling energization of the drive motors 22 and 23 to provide a strip drive velocity scheme which is illustrated in FIG. 2.

Whenever the number of frames through which the strip must be moved is less than a predetermined number n,, the strip is moved at a velocity V, that continuously decreases so as to be always in proportion to the number of frames f, through which the strip still remains to be moved, as illustrated at the right hand side of FiG. 2. Whenever the strip must be moved through more than said predetermined number n, of frames, it is moved at a relatively high but uniform velocity Vs through that number of framesf which is in excess of the value n and then, from the point at which the remaining number of frames to be moved is equal to n,, the film decelerates to maintain the proportioned relationship between V andfl.

Deceleration of the film is accomplished by so energizing the motor connected with the bobbin from which strip is being unwound that said motor effects some braking of its bobbin, while at the same time decreasing the energization of the other motor; hence assurance is bad that the film is always under some degree of lengthwise tension.

The computer 9 with which the electronic control apparatus is associated initially determines the number of frames through which the strip must be moved and the direction in which it must move in order to bring a desired frame to the reading station. The computer feeds this number and direction information into a frame counting register 31 and a direction register 32, respectively. Both of those registers are elements of the control apparatus 8. The proper drive motor is energized in accordance with a demand value that depends upon the numerical information in the frame counting register 3 I.

As the strip moves, the pulse signals that are produced as the code marks 26 pass the photocells 27 and 28 are delivered to a frame counting logic circuit 33 in which the form of the pulse signals is refined and by which the separate signals from the photocells 27 and 28 are unified and forwarded to the frame counting register to count it down. The logic circuit 33 also makes a logic decision whereby it continues to deliver pulse signals only until the strip has been moved through the number of frames called for by the computer, thus distinguishing from outputs of the photocells 27 and 28 that might be produced by back and forth movement of the selected frame as it is being centered at the reading station. The frame counting logic circuit also forwards its refined pulse signals to a true value transducer 34 and to a brake signal transducer 40, in each of which they are further processed.

In general, during energization of the drive motors to effect strip motion, the feed voltage with which they are energized, and which is supplied to them through a feed and brake control circuit 35,is obtained on the basis of balancing a demand value signal against a true value signal at a summation point 37. The true value signal is the output of the above mentioned true value transducer 34, produced on the basis of an output from the frame counting logic circuit 33. The demand value, which has the characteristic pattern illustrated by FIG. 2, is supplied to the summation point 37 by way of a feed phase switch 38 which is controlled by the frame counting register 31. During the rapid feed phase f, the feed phase switch supplies a constant value signal from the frame counting register to the summation point. During the decelerating phase f, the feed phase switch connects the summation point with a digital-toanalogue converter 39 to receive a changing demand value signal therefrom. The converter 39 is connected with the output of the frame counting register 3] and is arranged in a known manner to produce an analogue signal which varies with the status of the counting register, the output of the counting register being in binary form. However, the connection between the digital-to-analogue converter 39 and the frame counting register 31 is such that only binary numbers equal to or less than n, are transformed, so that the demand value signal from the converter 39 varies in accordance with the relationship between f and V, that is depicted in FIG. 2.

The brake signal transducer 40 is operative only during the phasef when the number of frames to be fed is equal to or less than n., and the linear velocity of the strip is steadily decreasing. During that phase, the velocity of the strip must be proportional to the number of frames remaining to be fed, and therefore the brake signal transducer 40 is connected with the frame counting register 31 to receive an input therefrom, as well as having an input from the frame counting logic circuit 33. The output of the brake signal transducer 40 is fed to the feed and brake control circuit 35, which directly controls energization of the drive motors 22 and 23. The feed and brake control circuit also receives an input from the direction register 32, as well as from the summation point 37.

When a frame is being held in the projection window 16, both drive motors are energized in their winding-on directions so that they maintain the strip under some tension to insure flatness of the frame being projected; and therefore the feed and brake control circuit 35 also receives an input from a frame holding circuit 36 which in turn receives input signals from the frame centering photocells 29 and 30.

When the desired frame is in register with the projection window 16, the frame counting register 31 will have been counted down to zero by means of the counting pulses from the frame counting logic circuit 33, and said logic circuit 33 and the brake signal transducer 40 are rendered inactive. At the same time the direction register 32 is set back to its zero or no direction" condition, and through its connection with the frame holding circuit 36 it in effect commands the latter to establish and maintain a position of the frame such that the frame centering photocells 29 and 30 are equally blanked by the code mark on the frame in the projection window, If there is an unequal blanking of the photocells 29 and 30, the frame holding circuit effects a correspondingly unequal energization of the drive motors, as required to return the frame to its centered position.

ELECTRONIC APPARATUS PARTICULAR DESCRIPTION With the foregoing general description of the electronic apparatus 8 as a background and outline, reference can now be made to FIG. 3 in connection with a more detailed consideration of that apparatus. FIG. 3 will be recognized as somewhat simplified, in that it includes only the elements of the apparatus that are essential to its operation. Certain matching units (such as inverters, impedance transformers and amplifiers) have been omitted where it has been possible to do so without encountering logic impossibilities. Those skilled in the art will readily understand the nature of the omitted elements and the manner of their connection in the illustrated circuit.

FRAME COUNTING LOGIC CIRCUIT 33 The light sensitive surface of the photocells 27 and 28 has a comparatively large extension, to eliminate the influence of dirt and the like that might be on the film; hence the code marks 26 will not instantaneously cover those photocells as they pass the same, with the result that the signal pulses emitted by the photocells in response to passage of the code marks will have oblique flanks rather than being true square pulses. The frame counting logic circuit 33 produces well defined pulses in response to signals emanating from the photocells 27 and 28v In general it comprises a pair of special bistable flip-flops 43 and 44, one connected with each of the photocells 27 and 28, a pair of inverters 45 and 46, one connected with each flip-flop, an AND-gate 47, and a second AND-gate 48.

Each of the flip-flops 43 and 44 can be a Schmitt trigger, which produces an output signal that has one or another of two defined values, depending upon whether its input signal is larger or smaller than a limit value which is settable on the flip-flop. This limit value is so chosen for each of the flip-flops 43 and 44 that the flip-flop is switched over when more than half of the light sensitive surface of its connected photocell 27 or 28 is blanked by a code mark 26.

The output signals from the flip-flops 43 and 44, which are respectively designated S, and 8,, comprise true square wave pulses as illustrated in lines b and c of FIG. 4, and can therefore be considered binary signals denoting either logic zero or logic one." Through the inverter 45 the output 5, of the flip-flop 43 is connected with one input of the AND-gate 47. The S, signal from the flip-flop 44 is similarly fed through the inverter 46 and thence to the other input terminal of the ANDgate 47. It will be evident that the AND-gate 47 puts out a "one signal whenever both S and S, are one; hence the output of that AND-gate has the same pattern as the 8, signal.

The output of AND-gate 47 is connected with one input terminal of the other AND-gate 48. The other input terminal of AND-gate 48 has a connection through a line 49 with the output of the frame counting register 31. If the condition of the register 31 is other than zero" (i.e., so long as the strip is required to be moved through one or more frames), the output of the register that is applied to the line 49 is binary one" and therefore the and" condition of the AND-gate 48 is fulfilled each time it receives an S signal. This is to say that so long as the frame counting register 31 signifies that frames must be counted, the AND-gate 48 delivers a one" pulse to that register each time a frame passes the reading station. Such pulses reduce the contents of the frame counting register one by one, down to zero, from the number initially set into it by the computer 9.

FRAME COUNTING REGISTER 31 AND FEED PHASE SWITCH 38 The frame counting register 31 comprises a plurality of bistable flip-flops that provide a binary counter 52. The counting register controls the feed phase switch 38, which comprises a pair of OR-gates 54 and 55.

The binary counter 52 is illustrated as consisting of 12 bistable flip-flops, arranged to respond to a numerically consecutive sequence of values, each double the value preceding it. The sequence starts with the value one" and thus represents the known geometric progression series 2, 2, 2 2 etc. The first five flipflops in the sequence, which together represent the value thirty-one," have their outputs connected with the input side of the OR-gate 54. The next seven bistable flip-flops of the counter have their outputs connected with the other OR-gate 55, the output of which is binary one" so long as the contents of the counter is 32 or more. The output 56 of the OR-gate 55 is connected with the summation point 37 and also with one input terminal of OR-gate 54. Hence the output ofOR- gate 54 will be binary one" so long as the contents of the counter represents any value greater than zero.

It will be apparent that at any moment the contents ofthe counter is signified by the conditions of its bistable flip-flops.

Through a connection 51 to the counter 52 the computer 9 sets into the counter a value signifying the ini tial number of frames through which the strip must be moved to bring a selected frame to the reading station. As already explained, the counter has a connection with the frame counting logic circuit 33 (and, specifcally, with the output of the AND-gate 48) by which the value thus set into it is reduced by one each time a frame passes the reading station.

The "one" output ofthe OR-gate 55 that is fed to the summation point 37 represents the velocity demand value S, for the rapid feed phasef and prevails as long as the number of frames through which the strip must be moved is in excess of SI, which is to say that n, in this case has the value 32, and switch over from the f. phase to the f, phase occurs when the contents of the counter 52 changes from 32 to 31.

During the f, phase the demand value signal is supplied to the summation point 37 from the digital-toanalogue converter 39.

DlGlTAL-TO-ANALOGUE CONVERTER 39 The outputs of the first five bistable flip-flops of the counter 52 are further connected to the digital-toanalogue converter 39, which is adapted to produce a direct current output that has a magnitude which varies in correspondence with the contents of the counter 52. The output side of the digital-analogue converter is connected to the summation point 37.

Since the contents of the counter 52 change step by step for numbers below 32, the magnitude of the output signal of the digital-analogue converter will correspondingly decrease in steps for values below 32, to provide a decreasing velocity demand value signal corresponding to S during the f, phase of strip movement.

During the maximum velocity phase f,, the output S, of the digital-analogue converter is superimposed upon the 8, output signal from the OR-gate 55 through an impedance adapter, and the actual S, signal therefore has the stepped configuration shown in the left-hand part of FIG. 5. However, for purposes of clarity, the scale of this stepped S, voltage is greatly exaggerated relative to the rest of the figure, since the output signal from the digital-analogue converter is of negligible size relative to the output signal from the OR-gate 55. Hence the true value of the S, signal at the summing point 37 is substantially equal to that designated by S, in FIG. 5.

During the f, phase, of course, the S, output signal is disconnected from the summing point by reason of the "or" condition no longer being satisfied at the OR-gate 55, and the demand value at the summation point 37 will consist only of the downwardly stepped output signal S, from the digital-analogue converter, which in FIG. can be regarded as more nearly shown to scale than the S, signal.

Since two consecutive binary inputs to the digitalanalogue converter effect only a small change in its output, its input is shown as connected with the first and second flip-flops of the counter 52 through an OR- gate 57.

TRUE VALUE TRANSDUCER 34 The true value transducer 34 comprises a derivating circuit consisting of four differentiating units 59, 60, 61 and 62, together with an OR-gate 64, a monostable flipflop 65 and an integrating circuit 66. Its function is to provide a true velocity value signal which is compared at the summation point 37 with the demand value signal from the OR-gate 55 or the digital-analogue converter 39.

Each of the differentiating units 59-62 comprises a circuit derivating on the front edge, that is, it is adapted to differentiate the front edge of an entering pulse and thus produce as its output a brief impulse. The outputs of the flip-flops 43 and 44 of the frame counting logic circuit 33 are respectively connected with the units 59, 60 for derivating on the front edge. The outputs of the inverters 45, 46 are likewise respectively connected with the units 61, 62 for derivating on the front edge. The four derivating units 59, 60, 61, 62 have their out puts connected with the four inputs of the OR-gate 64.

By derivating on the front edges of the signals 5, and S, of the flip-flops 43 and 44, as well as on the front edges of the inverses of those signals that are the outputs of their respective inverters 45 and 46, impulses are produced that correspond to both the front edge and the rear edge of each pulse signal S, and 8,. This is to say that there is an impulse for each end of each of the bars 260 and 26b associated with a frame, or four impulses per frame. These impulses are assembled in the OR-gate 64, the output of which thus has the pattern of impulses S, that is depicted at line d of FIG. 4.

The output of the OR-gate 64 is connected with the trigger input of the monostable flip-flop 65, which has a delay or recovery time 1'; hence for each impulse signal S; the monostable flip-flop 65 produces an output pulse S, having the width or duration r. The frequency of these pulses is in direct relation to the speed of the strip, and in the present case is equal to four times the number of frames per second passing the reading position.

The output of the monostable flip-flop 65 is connected with the input side of the integrator 66, and the output side of the latter is connected with the summation point 37. The integrator rectifies the pulsed input signal S, and produces a dc. output S. having a magnitude proportional to the strip velocity. The signal S is fed to the summation point as a true value and is there compared with demand value signals from the frame counting register 31 and the digital-to-analogue converter 39.

By varying the delay time T of the monostable flipflop 65, so as to vary the width (duration) of the pulse signals 8,, the magnitude of the true value signal S, can be varied in such manner as to influence the demand value signals S, and S,.

It will be apparent at this point that it would be possible to omit one of the photocells 27 or 28, together with the flip-flop and inverter that are connected with that photocell in the frame counting logic circuit 33. In that event the AND-gate 48 might be supplied with pulses from the monostable flip-flop 65 instead of from the AND-gate 47, and the connection between the flip-flop 65 and the integrator 66 would preferably include a pulse multiplier.

BRAKE SIGNAL TRANSDUCER 40 During the decelerating f phase the brake signal transducer 40 produces a true value brake signal that varies with the actual velocity of the strip so as to apply the greatest braking energization when the strip is moving fastest and thus achieve smooth deceleration. During the high velocity f, phase it produces no output.

The brake signal transducer comprises an AND-gate 69, a front edge derivating circuit 70, a monostable flip-flop 71 and an integrating circuit 72.

The AND-gate 69 has one of its input terminals connected with the monostable flip-flop 65 to receive the S, pulse signals therefrom, and its other input terminal is connected with the output line 56 from the 0R-gate 55 by way of an inverter 73. By reason of the inverter 73 in its input circuit, the and" condition of the AND gate 69 is satisfied only when the output of OR-gate 55 is binary "zero"; hence the AND-gate 69 passes pulse signals from the monostable flip-flop 65 only when the contents of the counter 52 is less than the value #1,.

These passed signals are derivated on the front edge by means of the differentiating circuit 70, and the resultant impulses are fed to the monostable flip-flop 71, which has a delay or restoration time of t, and which produces, as an output, signals that have the same frequency as the S impulse signals, but which are of a different duration than the S signals produced in response to those impulse signals.

The signals emanating from the monostable flip-flop 71 are fed to the integrator 72, which integrates them into a d.c. output having a magnitude that varies with the frequency and the width of the pulse signals fed into it. This d.c. is utilized as a brake signal, to control braking energization of the drive motor for the bobbin from which strip is being unwound.

In theory the S signals from the ()R-gate 64 could be directly applied to triggering the monostable flip-flop 71. However an impulse signal has a power so low that it is safest to load it with only one flip-flop, and it is for that reason that the flip-flop 71 is triggered as just explained.

As already indicated, no braking energization is applied to the motor for the unwinding bobbin during the high velocity phase f,. Instead, the inertia of that motor is relied upon to impose a slight drag upon its bobbin. Since the unwinding bobbin, due to the decreasing radius of the strip coil on it, is subjected to a steadily increasing speed of rotation for a constant lengthwise velocity of the strip, the acceleration of the unenergized motor for that bobbin will retard its rotation just enough to maintain a slight tension on the strip at all times.

DIRECTION REGISTER 32 AND FEED AND BRAKE CONTROL 35.

The direction register 32 comprises two bistable flipflops 75 and 76. It cooperates directly with the feed and brake control 35, which comprises switching means 81, 82, 83 and 84.

The computer 9 sets the flip-flop 75 to its binary one" condition when the increasing" motor 22 is to be energized for running in its forward direction, while the flip-flop 76 is set to binary one" by the computer when drive in the decreasing direction is required. The zeroing inputs of the flip-flops 75 and 76 are connected with the counter output line 49, so that whichever of those flip-flops has been set to one for a strip movement is reset back to its "zero condition when the contents of the counter 52 goes to zero.

The switching means 81 82, 83 and 84 that comprise the feed and brake control are in this case shown as field effect transistors. Those transistors have their output terminals connected with the input sides of amplifiers 78 and 79, which in turn have their outputs respectively connected with the motors 22 and 23.

The input side of the amplifier 78 is connected with two field effect transistors 81, 82, of which transistor 81 supplies an input to amplifier 78 for forward energization of the increasing" motor 22 while transistor 82 provides for braking energization of that motor. The input to amplifier 79 is likewise controlled by two field effect transistors 83, 84, of which transistor 83 controls forward energization of the "decreasing" motor while transistor 84 provides for control of its braking energization.

The output of the increasing flip-flop 75 is connected with the control elements of transistors 81 and 83, so that those transistors can conduct when the increasing" flip-flop is in its binary one" condition. Correspondingly, the output of the decreasing" flip-flop 76 is connected with the control elements of transistors 82 and 84.

The summation point 37 is connected with the input terminals of transistors 81 and 84, so that when either of those transistors conducts, the forward energizing current that it applies to its associated drive motor has a magnitude that corresponds to the difference between demand and true values at the summation point. The input terminals of transistors 83 and 82 are connected with the integrator 72 of the brake signal transducer 40; hence when either of those transistors conducts it causes a braking current to be applied to its associated motor, which current has a magnitude corresponding to the brake signal output of integrator 72,

It will now be apparent that when the increasing" flipflop is set to its binary "one" condition, the transistor 81 conducts to energize the increasing" motor 22 in its forward direction, and the magnitude of the energization of that motor is so controlled that its speed tends to be maintained in accordance with that signified by the demand value magnitude at the summation point 37. The same "one" setting of the increasing" flip-flop renders the transistor 83 conductive, but there is no potential on its input terminal until the beginning of the deceleration phase fr, after which it conducts a braking current to the "decreasing motor" 23 that is proportioned to the output of the integrator 72 of the brake signal transducer 40.

In like manner, setting the "decreasing flip-flop 76 to its binary "one" condition renders the transistor 84 conductive to feed forward energizing current to the decreasing" motor 23 from the summation point 37, and provides for braking energization of the "increasing" motor 22 during the deceleration phase, by way of the transistor 82.

FRAME HOLDING CIRCUIT 36 The frame holding circuit 36 functions only when the contents of the frame counting register is zero, that is, during the period f, (FIGS. 2 and 5) when a selected frame is at the reading station. The frame holding circuit 36, which serves to accurately center the frame at the reading station and to hold it there, comprises two additional field effect transistors 85 and 86, in cooperation with an inverter 91 and the frame centering photocells 29 and 30.

The transistors 85 and 86 have their output terminals respectively connected with the frame centering photocells 29 and 30. However, their control elements are connected with the output line 49 from the counting register 31, through the inverter 91; hence transistors 85 and 86 remain nonconducting until the counting register has been counted down to zero. They then apply energizing currents to the motors 22 and 23 as necessary to maintain equal areas of the photocells 29 and 30 blanked by end portions of the code mark 260 under the frame then in the reading position.

If for some reason the strip moving apparatus should get out of synchronization with the computer 9 that controls it, conformity between the computer and the strip moving apparatus can be reestablished automatically. The computer commands that the strip be fed to an end position, and by means of the special strip end marks mentioned above, in cooperation with a strip end control 92, the computer can be informed when it reaches the end position. The computer thereupon zeroes the frame counting register and conformity is reestablished.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides a method and means for rapidly advancing to a reading station any selected frame or segment on a strip of film or the like having a large number of such frames or segments at uniform intervals along its length, and for accurately centering the selected frame or segment exactly at the reading station and maintaining it thus centered. It will also be apparent that the invention provides for rapid, stead-speed movement of the strip during an initial phase of every transit thereof through more than a predetermined number of segments, and provides for a steadily decreasing velocity of the strip whenever the number of segments to be moved past the reading station is equal to or less than said number, the velocity of the strip then being proportioned to the number of segments through which it must still be moved.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims. I claim: 1. The method of controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length in order to bring the strip rapidly and accurately from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other segment is at said station, which method is characterized by:

A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude corresponding to the initial number of segments that must pass the station in order to bring the selected segment to the station; B. producing a pulse signal each time a segment passes the station; C. applying each pulse signal to the chargeable and dischargeable element in a manner to effect a proportionate reduction of the charge thereon so that at each instant the remaining charge thereon corresponds to the number of segments that must still pass the station; D. with the use of an output from said chargeable and dischargeable element, producing a demand value quantity 1. which has a substantially uniform magnitude for all segments above a predetermined number thereof that must pass the station and 2. which has a magnitude substantially directly proportional to the remaining number of segments that must pass the station whenever said remaining number of segments is less than said predetermined number;

E. with the use of said pulse signals, producing a true value quantity that has a magnitude corresponding to the prevailing speed of lengthwise motion of the strip;

F. whenever the strip is in motion, comparing said magnitude of said demand value quantity with said magnitude of said true value quantity; and

G. so energizing drive means for the strip, by reference to the difference between said demand and true value quantities, as to tend to maintain said difference at a predetermined value.

2. The method of claim 1, wherein the strip is driven by a pair of drive means, each energizable for propelling the strip in one direction of its motion and each also energizable to effect deceleration of the strip when it is moving in the direction in which it is propelled by the other drive means, wherein the step of energizing the drive means for the strip is further characterized by:

whenever the remaining number of segments that must pass the station is less than said predetermined number, energizing the appropriate drive means for strip deceleration with an energization magnitude that is substantially in proportion to the speed of the strip.

3. The method of controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length in order to bring the strip rapidly from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other one of said segments is at said station, which method is characterized by:

A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude corresponding to the initial number of segments that must be moved past the station in order to bring the selected segment to the station;

8. energizing a drive means for the strip in a manner to move the strip in the required lengthwise direction to carry the selected segment towards the station;

C. producing a pulse signal each time a segment passes the station;

D. applying each pulse signal to the chargeable and dischargeable element in a manner to effect a proportionate reduction of the charge thereon so that at each instant the remaining charge thereon corresponds to the number of segments that must still pass the station;

E. whenever, and for as long as, the charge on said element corresponds to a higher number than a predetermined number, producing a demand value signal having a substantially constant magnitude corresponding to a high speed of strip movement; whenever the charge on said element corresponds to a lower number than said predetermined number, producing a demand value signal having a magnitude which is in substantially direct propor tion to said charge and which corresponds to a velocity that decreases to zero in step with the number of segments that must still pass the station; G. utilizing the pulse signals to produce a true value signal having a magnitude which is comparabie to said magnitudes of the demand value signals and which corresponds to the prevailing lengthwise speed of the strip; and

H. at all times that a charge remains upon said element, controlling energization of the strip drive means in accordance with the difference between said magnitudes of the prevailing true and demand value signals and in a manner that tends to maintain said difference at a predetermined value.

4. The method of claim 3 wherein said drive means for the strip comprises a pair of reversible drive motors, each connected with one end of the strip, and switching means through which the motors can be selectively energized for forward and rearward operation, further characterized by:

I. at all times that the charge on said element corresponds to a lower number than said predetermined number, utilizing the pulse signals to produce a second true value signal having a magnitude which corresponds to the prevailing lengthwise speed of the strip;

J. at the times last mentioned, energizing for reverse operation the drive motor which is not producing lengthwise movement of the strip; and

K. at said last mentioned times, controlling the reverse-operation energization of the last mentioned drive motor in substantial correspondence with said magnitude of the second true value signal, to thereby maintain tension on the strip and impose upon it a retarding force that is substantially proportional to its lengthwise speed.

5v The method of claim 3, wherein the strip is driven by a pair of drive means, each energizable for propelling the strip in one direction of its motion and each also energizable to effect deceleration of the strip when it is moving in the direction in which it is propelled by the other drive means, further characterized by:

H. whenever the charge on said element corresponds to a lower number than said predetermined number, further utilizing the pulse signals to produce a controlled braking energization having a magnitude in proportion to the speed of the strip; and

I. applying said braking energization to the appropriate drive means for strip deceleration to insure that said difference between the magnitudes of the prevailing true and demand value signals will be maintained closely near its said predetermined value.

6. The method of so controlling energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse in minimum time and to stop accurately when it has been moved through the predetermined number of distance units, which method is characterized by:

A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude that corresponds to a predetermined number of distance units through which the member is to be moved;

8. producing a pulse signal each time the movable member traverses one distance unit;

C. each time a pulse signal is produced, effecting a discharge of the chargeable and dischargeable element that is of a magnitude corresponding to one distance unit, so that the remaining charge thereon has a magnitude corresponding to the number of distance units through which the movable member remains to be moved;

D. at all times that the movable member is in linear motion, producing a demand value signal that has a magnitude which depends upon the magnitude of the prevailing charge upon the chargeable and dischargeable element and which demand value signal magnitude is l. substantially constant whenever the magnitude of said prevailing charge corresponds to more than a fixed critical number of distance units and 2. substantially in direct proportion to the magnitude of the prevailing charge whenever that charge magnitude corresponds to less than the critical number of distance units; E. producing a true value signal that has a magnitude which is comparable to said magnitude of the demand value signal and which is substantially in proportion to the frequency of the pulse signals; and F. energizing the drive means by reference to the difference between said magnitudes of the demand value signal and the true value signal in a manner that tends to maintain said difference at a predetermined value. 7. Means for so controlling the energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse rapidly and to stop accurately when it has been moved through the predetermined number of distance units, said means comprising:

A. a chargeable and dischargeable element; B. means for impressing upon the chargeable and dischargeable element an initial charge having a magnitude that corresponds to a predetermined number of distance units through which the movable member is to be moved; C. pulse signal producing means comprising l. means operatively associated with the movable member to move in correspondence with its linear motion and 2. cooperating means at a fixed location, for producing a pulse signal each time the movable member traverses one distance unit;

D. discharge means connected with the pulse signal producing means and with the chargeable and dischargeable element for reducing the charge on said element by a magnitude corresponding to one distance unit each time a pulse signal is generated, so that the prevailing charge on said element always corresponds to the remaining number of distance units through which the movable member must still be moved;

E. first demand value signal means connected with the chargeable and dischargeable element and responsive to the charge thereon to produce a demand value signal that has a substantially constant magnitude whenever the magnitude of the prevailing charge on said element corresponds to more than a fixed critical number of distance units;

F. second demand value signal means connected with the chargeable and dischargeable element and responsive to the charge thereon to produce a variable demand value signal whenever the prevailing charge on said element corresponds to less than said critical number of distance units, and

which variable signal has a magnitude that is comparable to that of the first mentioned demand value signal but varies at a substantially constant ratio to the magnitude of the charge on said element;

G. true value signal means connected with the pulse signal producing means, for producing a true value signal having a magnitude comparable with said magnitudes of the signals produced by the demand value signal means and which varies in substantial correspondence with the frequency of the pulse signals;

H. means for producing an output signal having a magnitude corresponding to the difference between the prevailing true and demand value signals, the last named means being connected with said true value signal producing means and with said first and second demand value signal means; and

1. input means connected with the output signal producing means and with the drive means for the movable member, for controlling the energizing input to said drive means in accordance with the magnitude of the output signal and in a manner that tends to maintain that magnitude at a predetermined value.

8. The apparatus of claim 7 wherein the drive means for the linearly movable member comprises a pair of drive means, each energizable for propelling the movable member in one direction of its motion and also energizable to decelerate the movable member when it is moving in the direction in which it is propelled by the other, further characterized by:

J. means for producing a second true value signal that varies in substantial correspondence with the frequency of the pulse signals, the last mentioned means being connected with the pulse signal producing means and also so connected with the chargeable and dischargeable element as to produce the second true value signal only at times when the charge on the said element corresponds to less than said fixed critical number of distance units; and

K. means connected with the second true value signal producing means for applying to whichever of the drive means is appropriate for deceleration of the movable member an energization having a magnitude that is in substantially direct proportion to the second true value signal.

9. Means for controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length, so that the strip can be brought rapidly and accurately from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other segment is at said station, said means comprising:

A. a pair of drive motors, one for each end of the strip, each connected with its end of the strip;

B. switching means operatively associated with the drive motors for selecting a motor to be drivingly energized in accordance with the direction in which the strip is to be moved;

C. a plurality of detectable indicia on the strip, one for each segment, said indicia being in uniform relationship to their respective segments;

D. detector means at the station cooperable with said indicia to produce a pulse signal each time a segment passes the station;

E. a counter arranged to be impressed with a charge corresponding to a selected number and to be discharged in unit steps;

F. means for impressing upon the counter an initial charge corresponding to the initial number of segments through which the strip must be moved to bring the selected segment to the station;

G. means providing a connection between the detector means and the counter whereby pulse signals are impressed upon the counter to discharge it by a unit step each time a segment passes the station, so that the charge on the counter will at any instant correspond to the number of segments that must pass the station in order to bring a selected segment thereto;

H. first demand signal means connected with the counter to be operative only when charges on the counter correspond to more than a predetermined number of segments to pass the station and which, when operative, produces a first demand value signal having a magnitude which is substantially constant and which corresponds to a high speed of strip movement;

I. second demand signal means so connected with the counter and so arranged as to be operative when charges on the counter correspond to less than said predetermined number, to produce a variable demand value signal having a magnitude that is in substantially direct proportion to the charge on the counter;

J. true value signal producing means connected with the detector means for producing a true value signal having a magnitude which is comparable to the magnitudes of said first demand value signal and said variable demand value signal and which corresponds to the prevailing lengthwise speed of the strip as reflected in the frequency of the pulse signals; and

K. comparison means for comparing a demand value signal with a true value signal and for producing an output corresponding to the difference between them, said comparison means having an input terminal connected with both of the true value signal producing means and an output terminal connected with the switching means.

10. The apparatus of claim 9, further characterized L. controlled energizing means connected with said second demand signal means and with said switching means for impressing upon whichever drive motor is not drivingly energized a decelerating energization that has a magnitude which is in substantially direct proportion to said magnitude of the second demand value signal.

11. Means for so controlling the energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse rapidly and to stop accurately when it has been moved through the predetermined number of distance units, said means comprising:

A. a counter that can be charged with different charges, each corresponding to a predetermined number of distance units to be traversed by the member, and which counter can be discharged in unit increments by the application thereto of a pulse for each unit discharge;

B. demand value means cooperating with the counter to produce a demand value signal that persists steadily while there is a charge on the counter but has a magnitude which varies in dependence upon the charge on the counter;

C. pulse signal means cooperating with the linearly movable member and comprising detector means at a fixed location for producing pulse signals at a frequency which is in a fixed ratio to the rate at which the movable member traverses distance units;

D. means connected with said pulse signal producing means and with the counter for applying a pulse signal to the counter, to effect a unit incremental discharge thereof, each time the member traverses a distance unit;

E. means connected with said pulse signal means for producing uniform duration pulses at a frequency that varies in a fixed ratio to the frequency of the pulse signals;

F. means for integrating said pulses and for producing a true value signal that persists steadily while said member moves but has a magnitude that varies in correspondence with the frequency of the pulse signals; and

G. comparison means connected with said inte-grating means and with the demand value means for producing an energizing output having a magnitude which depends upon the difference in magnitudes of the true value and demand value signals, said comparison means having its output connected with the drive means.

12. The apparatus of claim 1!, further characterized by said means for producing uniform duration pulses comprising:

l. derivating means connected with the pulse signal means and responsive to the initiation of each pulse ofa pulse signal to produce an impulse, and

2. a monostable flip-flop having a predetermined recovery time and which is connected with said derivating means to be changed from its normal state to its alternate state in response to each impulse. 

1. The method of controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length in order to bring the strip rapidly and accurately from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other segment is at said station, which method is characterized by: A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude corresponding to the initial number of segments that must pass the station in order to bring the selected segment to the station; B. producing a pulse signal each time a segment passes the station; C. applying each pulse signal to the chargeable and dischargeable element in a manner to effect a proportionate reduction of the charge thereon so that at each instant the remaining charge thereon corresponds to the number of segments that must still pass the station; D. with the use of an output from said chargeable and dischargeable element, producing a demand value quantity
 1. which has a substantially uniform magnitude for all segments above a predetermined number thereof that must pass the station and
 2. which has a magnitude substantially directly proportional to the remaining number of segments that must pass the station whenever said remaining number of segments is less than said predetermined number; E. with the use of said pulse signals, producing a true value quantity that has a magnitude corresponding to the prevailing speed of lengthwise motion of the strip; F. whenever the strip is in motion, comparing said magnitude of said demand value quantity with said magnitude of said true value quantity; and G. so energizing drive means for the strip, by reference to the difference between said demand and true value quantities, as to tend to maintain said difference at a predetermined value.
 2. which has a magnitude substantially directly proportional to the remaining number of segments that must pass the station whenever said remaining number of segments is less than said predetermined number; E. with the use of said pulse signals, producing a true value quantity that has a magnitude corresponding to the prevailing speed of lengthwise motion of the strip; F. whenever the strip is in motion, comparing said magnitude of said demand value quantity with said magnitude of said true value quantity; and G. so energizing drive means for the strip, by reference to the difference between said demand and true value quantities, as to tend to maintain said difference at a predetermined value.
 2. The method of claim 1, wherein the strip is driven by a pair of drive means, each energizable for propelling the strip in one direction of its motion and each also energizable to effect deceleration of the strip when it is moving in the direction in which it is propelled by the other drive means, wherein the step of energizing the drive means for the strip is further characterized by: whenever the remaining number of segments that must pass the station is less than said predetermined number, energizing the appropriate drive means for strip deceleration with an energization magnitude that is substantially in proportion to the speed of the strip.
 2. a monostable flip-flop having a predetermined recovery time and which is connected with said derivating means to be changed from its normal state to its alternate state in response to each impulse.
 2. cooperating means at a fixed location, for producing a pulse signal each time the movable member traverses one distance unit; D. discharge means connected with the pulse signal producing means and with the chargeable and dischargeable element for reducing the charge on said element by a magnitude corresponding to one distance unit each time a pulse signal is generated, so that the prevailing charge on said element always corresponds to the remaining number of distance units through which the movable member must still be moved; E. first demand value signal means connected with the chargeable and dischargeable element and responsive to the charge thereon to produce a demand value signal that has a substantially constant magnitude whenever the magnitude of the prevailing charge on said element corresponds to more than a fixed critical number of distance units; F. second demand value signal means connected with the chargeable and dischargeable element and responsive to the charge thereon to produce a variable demand value signal whenever the prevailing charge on said element corresponds to less than said critical number of distance units, and which variable signal has a magnitude that is comparable to that of the first mentioned demand value signal but varies at a substantially constant ratio to the magnitude of the charge on said element; G. true value signal means connected with the pulse signal producing means, for producing a true value signal having a magnitude comparable with said magnitudes of the signals produced by the demand value signal means and which varies in substantial correspondence with the frequency of the pulse signals; H. means for producing an output signal having a magnitude corresponding to the difference between the prevailing true and demand value signals, the last named means being connected with said true value signal producing means and with said first and second demand value signal means; and I. input means connected with the output signal producing means and with the drive means for the movable member, for controlling the energizing input to said drive means in accordance with the magnitude of the output signal and in a manner that tends to maintain that magnitude at a predetermined value.
 2. substantially in direct proportion to the magnitude of the prevailing charge whenever that charge magnitude corresponds to less than the critical number of distance units; E. producing a true value signal that has a magnitude which is comparable to said magnitude of the demand value signal and which is substantially in proportion to the frequency of the pulse signals; and F. energizing the drive means by reference to the difference between said magnitudes of the demand value signal and the true value signal in a manner that tends to maintain said difference at a predetermined value.
 3. The method of controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length in order to bring the strip rapidly from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other one of said segments is at said station, which method is characterized by: A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude corresponding to the initial number of segments that must be moved past the station in order to bring the selected segment to the station; B. energizing a drive means for the strip in a manner to move the strip in the required lengthwise direction to carry the selected segment towards the station; C. producing a pulse signal each time a segment passes the station; D. applying each pulse signal to the chargeable and dischargeable element in a manner to effect a proportionate reduction of the charge thereon so that at each instant the remaining charge thereon corresponds to the number of segments that must still pass the station; E. whenever, and for as long as, the charge on said element corresponds to a higher number than a predetermined number, producing a demand value signal having a substantially constant magnitude corresponding to a high speed of strip movement; F. whenever the charge on said elEment corresponds to a lower number than said predetermined number, producing a demand value signal having a magnitude which is in substantially direct proportion to said charge and which corresponds to a velocity that decreases to zero in step with the number of segments that must still pass the station; G. utilizing the pulse signals to produce a true value signal having a magnitude which is comparable to said magnitudes of the demand value signals and which corresponds to the prevailing lengthwise speed of the strip; and H. at all times that a charge remains upon said element, controlling energization of the strip drive means in accordance with the difference between said magnitudes of the prevailing true and demand value signals and in a manner that tends to maintain said difference at a predetermined value.
 4. The method of claim 3 wherein said drive means for the strip comprises a pair of reversible drive motors, each connected with one end of the strip, and switching means through which the motors can be selectively energized for forward and rearward operation, further characterized by: I. at all times that the charge on said element corresponds to a lower number than said predetermined number, utilizing the pulse signals to produce a second true value signal having a magnitude which corresponds to the prevailing lengthwise speed of the strip; J. at the times last mentioned, energizing for reverse operation the drive motor which is not producing lengthwise movement of the strip; and K. at said last mentioned times, controlling the reverse-operation energization of the last mentioned drive motor in substantial correspondence with said magnitude of the second true value signal, to thereby maintain tension on the strip and impose upon it a retarding force that is substantially proportional to its lengthwise speed.
 5. The method of claim 3, wherein the strip is driven by a pair of drive means, each energizable for propelling the strip in one direction of its motion and each also energizable to effect deceleration of the strip when it is moving in the direction in which it is propelled by the other drive means, further characterized by: H. whenever the charge on said element corresponds to a lower number than said predetermined number, further utilizing the pulse signals to produce a controlled braking energization having a magnitude in proportion to the speed of the strip; and I. applying said braking energization to the appropriate drive means for strip deceleration to insure that said difference between the magnitudes of the prevailing true and demand value signals will be maintained closely near its said predetermined value.
 6. The method of so controlling energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse in minimum time and to stop accurately when it has been moved through the predetermined number of distance units, which method is characterized by: A. impressing upon a chargeable and dischargeable element an initial charge having a magnitude that corresponds to a predetermined number of distance units through which the member is to be moved; B. producing a pulse signal each time the movable member traverses one distance unit; C. each time a pulse signal is produced, effecting a discharge of the chargeable and dischargeable element that is of a magnitude corresponding to one distance unit, so that the remaining charge thereon has a magnitude corresponding to the number of distance units through which the movable member remains to be moved; D. at all times that the movable member is in linear motion, producing a demand value signal that has a magnitude which depends upon the magnitude of the prevailing charge upon the chargeable and dischargeable element and which demand value signal magnitude is
 7. Means for so controlling the energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse rapidly and to stop accurately when it has been moved through the predetermined number of distance units, said means comprising: A. a chargeable and dischargeable element; B. means for impressing upon the chargeable and dischargeable element an initial charge having a magnitude that corresponds to a predetermined number of distance units through which the movable member is to be moved; C. pulse signal producing means comprising
 8. The apparatus of claim 7 wherein the drive means for the linearly movable member comprises a pair of drive means, each energizable for propelLing the movable member in one direction of its motion and also energizable to decelerate the movable member when it is moving in the direction in which it is propelled by the other, further characterized by: J. means for producing a second true value signal that varies in substantial correspondence with the frequency of the pulse signals, the last mentioned means being connected with the pulse signal producing means and also so connected with the chargeable and dischargeable element as to produce the second true value signal only at times when the charge on the said element corresponds to less than said fixed critical number of distance units; and K. means connected with the second true value signal producing means for applying to whichever of the drive means is appropriate for deceleration of the movable member an energization having a magnitude that is in substantially direct proportion to the second true value signal.
 9. Means for controlling lengthwise motion of an information carrier strip having defined uniformly spaced segments along its length, so that the strip can be brought rapidly and accurately from a position in which one of said segments is at a defined relatively fixed station to a position at which any selected other segment is at said station, said means comprising: A. a pair of drive motors, one for each end of the strip, each connected with its end of the strip; B. switching means operatively associated with the drive motors for selecting a motor to be drivingly energized in accordance with the direction in which the strip is to be moved; C. a plurality of detectable indicia on the strip, one for each segment, said indicia being in uniform relationship to their respective segments; D. detector means at the station cooperable with said indicia to produce a pulse signal each time a segment passes the station; E. a counter arranged to be impressed with a charge corresponding to a selected number and to be discharged in unit steps; F. means for impressing upon the counter an initial charge corresponding to the initial number of segments through which the strip must be moved to bring the selected segment to the station; G. means providing a connection between the detector means and the counter whereby pulse signals are impressed upon the counter to discharge it by a unit step each time a segment passes the station, so that the charge on the counter will at any instant correspond to the number of segments that must pass the station in order to bring a selected segment thereto; H. first demand signal means connected with the counter to be operative only when charges on the counter correspond to more than a predetermined number of segments to pass the station and which, when operative, produces a first demand value signal having a magnitude which is substantially constant and which corresponds to a high speed of strip movement; I. second demand signal means so connected with the counter and so arranged as to be operative when charges on the counter correspond to less than said predetermined number, to produce a variable demand value signal having a magnitude that is in substantially direct proportion to the charge on the counter; J. true value signal producing means connected with the detector means for producing a true value signal having a magnitude which is comparable to the magnitudes of said first demand value signal and said variable demand value signal and which corresponds to the prevailing lengthwise speed of the strip as reflected in the frequency of the pulse signals; and K. comparison means for comparing a demand value signal with a true value signal and for producing an output corresponding to the difference between them, said comparison means having an input terminal connected with both of the true value signal producing means and an output terminal connected with the switching means.
 10. The apparatus of claim 9, further characterized by: L. conTrolled energizing means connected with said second demand signal means and with said switching means for impressing upon whichever drive motor is not drivingly energized a decelerating energization that has a magnitude which is in substantially direct proportion to said magnitude of the second demand value signal.
 11. Means for so controlling the energization of drive means for a linearly movable member that must from time to time be traversed through different but predetermined numbers of uniform distance units as to cause the member to accomplish each traverse rapidly and to stop accurately when it has been moved through the predetermined number of distance units, said means comprising: A. a counter that can be charged with different charges, each corresponding to a predetermined number of distance units to be traversed by the member, and which counter can be discharged in unit increments by the application thereto of a pulse for each unit discharge; B. demand value means cooperating with the counter to produce a demand value signal that persists steadily while there is a charge on the counter but has a magnitude which varies in dependence upon the charge on the counter; C. pulse signal means cooperating with the linearly movable member and comprising detector means at a fixed location for producing pulse signals at a frequency which is in a fixed ratio to the rate at which the movable member traverses distance units; D. means connected with said pulse signal producing means and with the counter for applying a pulse signal to the counter, to effect a unit incremental discharge thereof, each time the member traverses a distance unit; E. means connected with said pulse signal means for producing uniform duration pulses at a frequency that varies in a fixed ratio to the frequency of the pulse signals; F. means for integrating said pulses and for producing a true value signal that persists steadily while said member moves but has a magnitude that varies in correspondence with the frequency of the pulse signals; and G. comparison means connected with said inte-grating means and with the demand value means for producing an energizing output having a magnitude which depends upon the difference in magnitudes of the true value and demand value signals, said comparison means having its output connected with the drive means.
 12. The apparatus of claim 11, further characterized by said means for producing uniform duration pulses comprising: 